Atividade antioxidante e antimicrobiana de produtos naturais e seus efeitos na associação com conservantes sintéticos de alimentos e cosméticos

Abstract

The demand for products free of synthetic preservatives it has increased every day. Some natural products such as vegetable and essential oils have in their composition substances that act as agents in the prevention of oxidation, stabilization of free radicals and for inhibiting micro-organisms, indicating a great conservation potential. This study aimed to evaluate the antioxidant and antimicrobial activity of natural products and check a possible synergistic effect against pathogenic micro-organisms when tested in combination with synthetic food and cosmetic preservatives. Were evaluated essential oils citronella (Cymbopogon nardus), clove (Syzygium aromaticum), eucalyptus (Eucalyptus globulus), lavender (Lavandula angustifolia) and laurel (Laurus nobilis), and also the vegetable extracted from pomegranate seed oil. The synthetic preservatives utilized were methylparaben and sodium metabisulfite. The antioxidant activity of the oil was determined by DPPH method. The antimicrobial activity was determined by Minimum Inhibitory Concentration techniques (MIC) and Minimum Bactericidal Concentration (MBC), and oil association tests with synthetic preservative through the technique of "checkerboard" front Gram-positive bacteria, Bacillus cereus and Staphylococcus aureus and Gram-negative bacteria, Escherichia coli and Salmonella typhi. Among the analyzed oils, essential oil of cloves had the highest antioxidant activity (IC50: 0,008 mg.mL-1) considered a very strong antioxidant action, followed by laurel oils (IC50: 0,24 mg.mL-1) , citronella (IC50: 0,99 mg.mL-1) vegetable oil and pomegranate seed (IC50: 2.32 mg.mL-1) with a weak antioxidant activity. In the determination of antimicrobial activity, lavender and laurel oils showed similar results, both with MIC 5.0 mg.mL-1. The essential oils of citronella and clove showed the lowest inhibitory concentrations (1.25 and 2.5 mg.mL-1) for almost all strains tested, which were associated with the synthetic preservatives. The presence of synergism was observed only in the combination of the essential oil of clove and methylparaben on the bacteria Escherichia coli and Salmonella typhi, reducing the MIC of the preservative in the presence of low concentrations of the essential oil. Thus, it is concluded that the clove essential oil consists of a natural product with excellent properties for possible conservation as a food condiment or cosmetics.